Electrode active material, preparation method thereof, and electrode and lithium battery containing the same

ABSTRACT

An electrode active material includes a core capable of intercalating and deintercalating lithium; and a surface treatment layer disposed on at least a portion of a surface of the core, wherein the surface treatment layer includes a lithium-free oxide having a spinel structure, and an intensity of an X-ray diffraction peak corresponding to impurity phase of the lithium-free oxide, when measured using Cu—Kα radiation, is at a noise level of an X-ray diffraction spectrum or less.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of Korean PatentApplication No. 10-2011-0115365, filed on Nov. 7, 2011, and all thebenefits accruing therefrom under 35 U.S.C. § 119, the content of whichis incorporated herein in its entirety by reference.

BACKGROUND

1. Field

The present disclosure relates to an electrode active material, apreparation method thereof, and an electrode and a lithium batteryincluding the same.

2. Description of the Related Art

For smaller and higher performance devices, it is important to increasethe energy density of a lithium battery, in addition to decreasing thesize and weight thereof. That is, a higher-voltage and higher-capacitylithium battery would be desirable.

To provide a lithium battery satisfying these desires, research is beingconducted on cathode active materials having high voltage and highcapacity.

When typical cathode active materials having high voltage and highcapacity are used, side reactions, such as elution of a transition metaland generation of gas, occur at a high temperature and/or a voltagehigher than about 4.4 V. Due to these side reactions, the performance ofa battery is degraded in a high temperature and high voltageenvironment.

Therefore, there remains a need for improved methods of preventingdegradation of a battery in a high temperature and high voltageenvironment.

SUMMARY

Provided is an electrode active material capable of substantially oreffectively preventing performance degradation of a battery under hightemperature and high voltage conditions.

Provided is an electrode including the electrode active material.

Provided is a lithium battery including the electrode.

Provided are methods of manufacturing the electrode active material.

Additional aspects, features, and advantages will be set forth in partin the description which follows and, in part, will be apparent from thedescription.

According to an aspect, an electrode active material includes a corecapable of intercalating and deintercalating lithium; and a surfacetreatment layer disposed on at least a portion of a surface of the core,wherein the surface treatment layer may include a lithium-free oxidehaving a spinel structure, and an intensity of an X-ray diffraction peakcorresponding to an impurity phase of the lithium-free oxide, whenmeasured using Cu—Kα radiation, is at a noise level of an X-raydiffraction spectrum or less.

According to another aspect, an electrode includes the electrode activematerial.

According to another aspect, a lithium battery includes the electrode.

According to another aspect, a method of manufacturing an electrodeactive material includes contacting a core including an electrode activematerial and a lithium-free oxide having a spinel structure; and forminga surface treatment layer including the lithium-free oxide on the coreby a dry process to manufacture the electrode active material.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings in which:

FIGS. 1A and 1B are graphs of intensity (arbitrary units, a.u.) versusscattering angle (degrees two-theta, 28) which illustrate a result ofX-ray diffraction (XRD) analysis of SnZn₂O₄ manufactured according toComparative Preparation Example 1, and Preparation Example 1,respectively;

FIG. 2 illustrates a scanning electron microscope (SEM) image of aSnZn₂O₄ prepared in Preparation Example 1;

FIG. 3 illustrates an SEM image of LiNi_(0.5)Mn_(1.5)O₄ powder used inExample 1;

FIG. 4 illustrates an SEM image of a cathode active materialmanufactured in Example 1; and

FIG. 5 is a graph of capacity retention (percent, %) versus C-rate whichillustrates the discharge rate characteristics of lithium batteriesmanufactured according to Examples 97 to 98 and Comparative Example 5;and

FIG. 6 is a schematic diagram illustrating a lithium battery accordingto an embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings, wherein like referencenumerals refer to like elements throughout. In this regard, the presentembodiments may have different forms and should not be construed asbeing limited to the descriptions set forth herein. Accordingly, theembodiments are merely described below, by referring to the figures, toexplain aspects of the present description.

It will be understood that when an element is referred to as being “on”another element, it can be directly on the other element or interveningelements may be present therebetween. In contrast, when an element isreferred to as being “directly on” another element, there are nointervening elements present.

It will be understood that, although the terms “first,” “second,”“third” etc. may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer or section from another element, component, region, layer, orsection. Thus, “a first element,” “component,” “region,” “layer,” or“section” discussed below could be termed a second element, component,region, layer or section without departing from the teachings herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms, including “at least one,” unless the content clearly indicatesotherwise. “Or” means “and/or.” As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. It will be further understood that the terms “comprises”and/or “comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may, typically, have rough and/or nonlinear features. Moreover,sharp angles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

“Transition metal” means a metal of Groups 3 to 12 of the Periodic Tableof the Elements.

“Rare earth” means the fifteen lanthanide elements, i.e., atomic numbers57 to 71, plus scandium and yttrium.

Hereinafter, an electrode active material, a manufacturing methodthereof, and an electrode and a battery including the same, according toan exemplary embodiment, will be disclosed in further detail.

An electrode active material according to an embodiment includes a corecapable of intercalating and deintercalating lithium; and a surfacetreatment layer disposed (e.g., formed) on at least a portion of thecore, wherein the surface treatment layer includes a lithium-free oxidehaving a spinel structure, and an intensity of an X-ray diffraction(XRD) peak corresponding to an impurity phase of the lithium-free oxide,when measured using Cu—Kα radiation, is at a noise level of an XRDspectrum or less. The fact that intensities of diffraction peaks of theimpurity phases in the XRD spectrum are at the noise level or lessindicates that practically no peaks for the impurity phases are detectedsince the intensities of the diffraction peaks are less than the noiselevel which forms a baseline. The noise level refers to x-ray scatteringthat occurs due to scattering in the surrounding environment such as inair, water, etc. irrelevant from the scattering obtained from a targetmaterial. The noise level may be determined as the average peakintensity of peaks not corresponding to the core or the surfacetreatment layer.

That is, because at least a portion of a surface of the core capable ofintercalating and deintercalating lithium is treated withspinel-structured lithium-free oxide practically having no impurityphases, the surface treatment layer may be formed on at least a portionof or on an entirety of the surface of the core. The term “surfacetreatment layer” may also refer to a coating layer as will be understoodby a person of ordinary skill in the art. The impurity phase refers toany phase except the spinel phase of the surface treatment layer or acompound of the core.

Since the lithium-free oxide having a spinel structure practically hasno impurity phases, a side reaction due to impurity phases during acharge/discharge process may be suppressed.

Hereinafter, unless stated otherwise, a lithium-free oxide having aspinel structure is an oxide in which impurity phases are substantiallynot present and/or removed and in which lithium is not substantiallypresent, e.g., contained in an amount of less than 1 wt %, specificallyless than 0.1 wt %.

The lithium-free oxide having a spinel structure may be highlycrystalline. That is, the lithium-free oxide having a spinel structurehas a spinel structure, as may be determined in the XRD spectrum usingCu—Kα radiation, and may have a sharper diffraction peak compared tothat of a less crystalline lithium-free oxide. As the lithium-free oxidehas a high crystalline property, stability of an electrode activematerial at high voltage may be increased.

For example, the lithium-free oxide has a diffraction peak at about35.5°±2.0° two-theta (2θ) for a peak corresponding to a (311) crystalface, when measured using Cu—Kα radiation, and a full width at halfmaximum (FWHM) of the diffraction peak may be less than 0.3° 2θ. Forexample, the lithium-free oxide may have a diffraction peak at about35.5°±2.0° 2θ for the peak corresponding to the (311) face, whenmeasured using Cu—Kα radiation, and a FWHM of the diffraction peak mayrange from about 0.220° to about 0.270° 2θ.

The spinel-structured lithium-free oxide does not substantiallyintercalate and deintercalate lithium, and thus, does not directlycontribute to a battery capacity. Therefore, the surface treatment layerincluding the oxide may serve, for example, as a protective layer of thecore. That is, the surface treatment layer may serve to suppress a sidereaction between the core and an electrolyte. The surface treatmentlayer may also serve to substantially or effectively prevent atransition metal from being removed from the core, which is capable ofintercalating and deintercalating lithium.

Any high crystalline spinel-structured oxide having no impurity phasesand including two or more metals, except for lithium, or metalloidelements may be used as the spinel-structured lithium-free oxide. Themetalloid can be one or more selected from B, Si, Ge, As, Sb, and Te.

The spinel-structured lithium-free oxide has a stronger metal-oxygenbond in comparison to an oxide having a halite crystal structure, forexample, NaCl, CaO, and FeO, or an oxide having a corundum crystalstructure, for example, Al₂O₃, Fe₂O₃, FeTiO₃, and MgO. Therefore, astable surface treatment layer may be formed which is stable under hightemperature and high voltage conditions.

For example, the lithium-free oxide may be one or more selected fromoxides expressed by the following Formula 1:AM^(a) ₂O₄,  Formula 1wherein A is one or more selected from tin (Sn), magnesium (Mg),molybdenum (Mo), copper (Cu), zinc (Zn), titanium (Ti), nickel (Ni),calcium (Ca), iron (Fe), vanadium (V), lead (Pb), cobalt (Co), germanium(Ge), cadmium (Cd), mercury (Hg), strontium (Sr), manganese (Mn),aluminum (Al), tungsten (W), and beryllium (Be), M^(a) is one or moreselected from Mg, Zn, Al, V, Mn, gallium (Ga), chromium (Cr), Fe,rhodium (Rh), Ni, indium (In), Co, and Mn, and A is different fromM^(a).

For example, the lithium-free oxide may be one or more selected fromSnMg₂O₄, SnZn₂O₄, MgAl₂O₄, MoAl₂O₄, CuAl₂O₄, ZnAl₂O₄, ZnV₂O₄, TiMn₂O₄,ZnMn₂O₄, NiAl₂O₄, MgGa₂O₄, ZnGa₂O₄, CaGa₂O₄, TiMg₂O₄, VMg₂O₄, MgV₂O₄,FeV₂O₄, ZnV₂O₄, MgCr₂O₄, MnCr₂O₄, FeCr₂O₄, CoCr₂O₄, NiCr₂O₄, CuCr₂O₄,ZnCr₂O₄, CdCr₂O₄, TiMn₂O₄, ZnMn₂O₄, MgFe₂O₄, TiFe₂O₄, MnFe₂O₄, CoFe₂O₄,NiFe₂O₄, CuFe₂O₄, ZnFe₂O₄, CdFe₂O₄, AlFe₂O₄, PbFe₂O₄, MgCo₂O₄, TiCo₂O₄,ZnCo₂O₄, SnCo₂O₄, FeNi₂O₄, GeNi₂O₄, MgRh₂O₄, ZnRh₂O₄, TiZn₂O₄, SrAl₂O₄,CrAl₂O₄, MoAl₂O₄, FeAl₂O₄, CoAl₂O₄, MgGa₂O₄, ZnGa₂O₄, MgIn₂O₄, CaIn₂O₄,FeIn₂O₄, CoIn₂O₄, NiIn₂O₄, CdIn₂O₄, and HgIn₂O₄.

For example, the lithium-free oxide may be one or more selected fromSnMg₂O₄, SnZn₂O₄, MgAl₂O₄, CuAl₂O₄, ZnAl₂O₄, and NiAl₂O₄.

For example, the lithium-free oxide may be one or more selected fromSnMg₂O₄, SnZn₂O₄, and MgAl₂O₄.

The lithium-free oxide may have a ratio of an intensity of an X-raydiffraction peak corresponding to a (440) crystal face to an intensityof an X-ray diffraction peak corresponding to a (311) crystal face,i.e., I(440)/I(311), of about 0.3 or more, specifically about 0.3 toabout 5, more specifically about 0.5 to about 3, in an XRD spectrum ofthe lithium-free oxide. For example, the I(440)/I(311) may range fromabout 0.3 to about 0.7.

Also, in an XRD spectrum of the lithium-free oxide, a ratio of anintensity of an X-ray diffraction peak corresponding to a (511) crystalface to an intensity of an X-ray diffraction peak corresponding to a(311) crystal face, i.e., I(511)/I(311), may be about 0.25 or more,specifically about 0.3 to about 5, more specifically about 0.5 to about3. For example, the I(511)/I(311) may range from about 0.25 to about0.5.

Also, in an XRD spectrum of the lithium-free oxide, a ratio of anintensity of a peak corresponding to a (511) crystal face to anintensity of a peak corresponding to a (440) crystal face, i.e.,I(511)/I(440), may be about 0.5 or more, specifically about 0.6 to about5, more specifically about 0.5 to about 3. For example, theI(511)/I(440) may range from about 0.5 to about 0.9.

The content of the lithium-free oxide may be about 10 weight percent (wt%) or less, for example, about 5 wt % or less, specifically about 0.1 wt% to about 10 wt %, based on the total weight of the electrode activematerial. For example, the content of the lithium-free oxide may be 0 toabout 10 wt %. For example, the content of the lithium-free oxide may be0 to about 5 wt %.

The surface treatment layer of the electrode active material may includeone or more, and in an embodiment two or more, elements selected from ametal and metalloid with an atomic weight of 9 or more, and the surfacetreatment layer may comprise one or more selected from Sn, Mg, Mo, Cu,Zn, Ti, Ni, Ca, Al, V, Mn, Ga, Fe, Cr, Rh, In, Pb, Co, Ge, Cd, Hg, Sr,W, and Be.

A content of the metal and/or the metalloid with an atomic weight of 9or more of the surface treatment layer may be about 10 wt % or less, forexample, may be 0 to about 10 wt %, specifically about 0.1 wt % to about8 wt %, based on the total weight of the electrode active material. Forexample, the metal and/or the metalloid may be contained in an amount of0 to about 6 wt %.

A composition ratio of oxygen to the metal and/or metalloid of thesurface treatment layer, which may be selected from a metal and ametalloid with an atomic weight of 9 or more, may be about 4:2.1 toabout 4:3.9. For example, the composition ratio of oxygen to the metalor metalloid may be about 4:2.5 to about 4:3.5. For example, thecomposition ratio of oxygen to the metal or metalloid may be about 4:2.9to about 4:3.1. For example, the composition ratio of oxygen to themetal or metalloid may be about 4:3. The composition ratio correspondsto a composition ratio of oxygen to (A+M^(a)) in the lithium-free oxideincluded in the surface treatment layer and having a composition of theformula AM^(a) ₂O₄.

A thickness of the surface treatment layer of the electrode activematerial may range from about 1 angstrom (Å) to about 1 micrometer (μm).For example, the thickness of the surface treatment layer may range fromabout 1 nanometer (nm) to about 100 nm. For example, the thickness ofthe surface treatment layer may range from about 1 nm to about 30 nm.

The surface treatment layer on the electrode active material may beformed by completely covering the core or by partially being formed onthe core, e.g., to form an island, for example.

An average particle diameter of the core of the electrode activematerial may be about 10 nm to about 50 μm. For example, the averageparticle diameter of the core may be about 10 nm to about 30 μm. Forexample, the average particle diameter of the core may be about 1 μm toabout 30 μm.

The core is capable of intercalating and deintercalating lithium in theelectrode active material and may include a cathode active material. Thecathode active material may be lithium transition metal oxide. Anylithium transition metal oxide for a cathode of a lithium battery whichis used in the art may be used as the lithium transition metal oxide.For example, the lithium transition metal oxide may have a spinelstructure or a layered structure.

The lithium transition metal oxide may be a single composition, or acompound or a composite of two or more compounds. For example, thelithium transition metal oxide may be a composite of two or morecompounds, each having a layered-structure. For example, the lithiumtransition metal oxide may be a composite of a compound having alayered-structure and a compound having a spinel-structure.

For example, the lithium transition metal oxide may include anover-lithiated oxide (OLO) or a lithium transition metal oxide with anaverage operating voltage about 4.3 V or higher. For example, an averageoperating voltage of the lithium transition metal oxide may range fromabout 4.3 V to about 5.0 V.

The average operating voltage means a value obtained by dividing acharge/discharge electric energy by a charge/discharge quantity ofelectricity when a battery is charged and discharged to an upper limitand a lower limit of a charge/discharge voltage at a selected operatingvoltage of the battery.

The core may include, for example, a compound expressed by the followingFormulas 2 and 4:Li[Li_(a)Me_((1−a))]O_((2+d)), and  Formula 2Li[Li_(b)Me_(c)M′_(e)]O_((2+d))  Formula 3wherein 0<a<1, (b+c+e)=1; 0<b<1, 0<e<0.1; 0≤d≤0.1, Me is one or moremetals selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al, Mg, Zr, and B,and M′ is one or more metals selected from Mo, W, Ir, Ni, and Mg. Forexample, 0<a<0.33.

Also, the core may include compounds expressed by the following Formulas4 to 8:Li_(x)Co_((1−y))M_(y)O_((2−α))X_(α),  Formula 4Li_(x)Co_((1−y−z))Ni_(y)M_(z)O_((2−α))X_(α),  Formula 5Li_(x)Mn_((2−y))M_(y)O_((4−α))X_(α),  Formula 6Li_(x)Co_((2−y))M_(y)O_(4−α)X_(α), and  Formula 7Li_(x)Me_(y)M_(z)PO_((4−α))X_(α),  Formula 8wherein 0.90≤x≤1.1, 0≤y≤0.9, 0≤z≤0.5, (1−y−z)>0, 0≤α≤2, Me is one ormore metals selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al, Mg, Zr, andB, M is at least one element selected from Mg, Ca, Sr, Ba, Ti, Zr, Nb,Mo, W, Zn, Al, Si, Ni, Mn, Cr, Fe, Mg, Sr, V, and a rare-earth element,and X is an element selected from O, F, S, and P.

Also, the core may include compounds expressed by the following Formulas9 and 10:(Li₂MO₃)_(p)—(LiMeO₂)_((1−p)), and  Formula 9(Li₂MO₃)_(x)—(LiMeO₂)_(y)—(Li_(1+d)M′_(2−d)O₄)_(z)  Formula 10wherein 0<p<1, x+y+z=1; 0<x<1, 0<y<1, 0<z<1; 0≤d≤0.33, M is one or moremetals selected from Mg, Ca, Sr, Ba, Ti, Zr, Nb, Mo, W, Zn, Al, Si, Ni,Mn, Cr, Fe, Mg, Sr, V, and a rare-earth element, Me is one or moremetals selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al, Mg, Zr, and B,and M′ is one or more metals selected from Ti, V, Cr, Mn, Fe, Co, Ni,Cu, Al, Mg, Zr, and B.

A compound of Formula 9 may have a layered-structure, the Li₂MO₃ and theLiMeO₂ of Formula 10 may have a layered-structure, and theLi_(1+d)M′_(2−d)O₄ of Formula 10 may have a spinel-structure.

The core capable of charging and discharging lithium in the electrodeactive material may include anode active material. The anode activematerial may include one or more selected from lithium metal, a metalwhich is alloyable with lithium, a transition metal oxide, anon-transition metal oxide, and a carbonaceous material. Any anodeactive material for a lithium battery which is used in the art may beused as the anode active material.

For example, the metal, which is alloyable with lithium, may compriseone or more selected from Si, Sn, Al, Ge, Pb, Bi, Sb, a Si—Y alloywherein Y is one or more selected from an alkali metal, an alkali earthmetal, a Group 13 element, a Group 14 element, a transition metal, and arare-earth metal, (other than Si), and an Sn—Y alloy wherein Y is one ormore selected from an alkali metal, alkali earth metal, a Group 13element, a Group 14 element, a transition metal, and a rare-earth metal(other than Sn). The element Y may comprise one or more selected fromMg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg,Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B,Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, and Po.

For example, the transition metal oxide may comprise one or moreselected from lithium titanium oxide, vanadium oxide, and lithiumvanadium oxide.

For example, the non-transition metal oxide may comprise one or moreselected from SnO₂ or SiO_(x) (0<x<2).

The carbonaceous material may comprise one or more selected fromcrystalline carbon, and an amorphous carbon. The crystalline carbon maycomprise one or more selected from natural graphite of amorphous type,plate type, flake type, spherical type, or fiber type, and syntheticgraphite. The amorphous carbon may comprise one or more selected fromsoft carbon (low-temperature-sintered carbon), hard carbon, mesophasepitch carbide, and sintered coke.

The surface treatment layer of the electrode active material may beformed on a surface of a core by mechanically applying energy with a dryprocess after contacting (e.g., mixing) a precursor of thespinel-structured lithium-free oxide and the core.

An electrode according to an embodiment may include the electrode activematerial described above. The electrode may be a cathode or an anode.

The cathode may be manufactured as follows.

A cathode active material composition may be prepared by contacting(e.g., mixing) a cathode active material having a surface treatmentlayer formed on at least a portion of a surface thereof, a conductingagent, a binder, and a solvent. The cathode active material compositionmay be directly coated on an aluminum current collector and dried formanufacturing a cathode plate on which a cathode active layer is formed.Alternatively, the cathode active material composition may be cast on aseparate support, and then a film peeled from the support is laminatedon an aluminum current collector for manufacturing a cathode plate onwhich a cathode active layer is formed.

As the conducting agent, carbon black, natural graphite, artificialgraphite, acetylene black, ketjen black, carbon fiber; a metal powder,metal fiber, or metal tube such as carbon nanotube, copper, nickel,aluminum, and silver; and a conductive polymer such as polyphenylenederivatives may be used; however, the conducting agent is not limitedthereto, and any conducting agent used in the art may be used.

As the binder, vinylidene fluoride/hexafluoropropylene co-polymer,polyvinylidene fluoride (PVDF), polyacrylonitrile, poly(methylmethacrylate), polytetrafluoroethylene (PTFE), mixture of the foregoingpolymers, and styrene butadiene rubber polymer may be used, and as thesolvent, N-methylpyrrolidone (NMP), acetone, and water may be used;however, the solvent is not limited thereto, and any material used inthe art may be used. Contents of the cathode active material, theconducting agent, the binder, and the solvent may be selected so as tobe suitable for use in a lithium battery.

The anode may be manufactured using the same method as that used for thecathode except that an anode active material instead of a cathode activematerial is used.

For example, the anode may be manufactured as follows.

An anode active material composition may be manufactured by contacting(e.g., mixing) an anode active material having a surface treatment layerformed on at least a portion of a surface thereof, a conducting agent, abinder, and a solvent. The anode active material composition may bedirectly coated on a copper current collector for manufacturing an anodeplate. Alternatively, the anode active material composition may be caston a separate support, and then an anode active material film peeledfrom the support is laminated on a copper current collector tomanufacture an anode plate.

The same conducting agent, binder, and solvent as in the cathode may beused for the anode active material. If desired, a plasticizer may beadded to the cathode active material composition and the anode activematerial composition to form pores in an electrode plate.

Contents of the anode active material, the conducting agent, the binder,and the solvent may be selected to be suitable for use in a lithiumbattery. According to use and structure of a lithium battery, one ormore of the conducting agent, the binder, and the solvent may be omittedif desired.

A lithium battery according to an embodiment may comprise the electrode.The lithium battery, for example, may be manufactured as follows.

First, a cathode and an anode according to an embodiment aremanufactured as described above. One or more of the cathode and anodeinclude an electrode active material of which a surface treatment layerincluding a lithium-free oxide having a spinel structure and having noimpurity phases is formed on a core capable of intercalating anddeintercalating lithium.

Next, a separator to be inserted between the cathode and the anode isprovided. Any separator typically used for a lithium battery may beused. A separator which has low resistance to ion movement and has anexcellent ability in containing an electrolyte solution may be used. Forexample, the separator may comprise at least one selected from glassfiber, polyester, Teflon, polyethylene, polypropylene, and PTFE, whereinthe selected separator may be a non-woven fiber type or a woven fibertype separator. For example, a windable separator such as polyethyleneand polypropylene may be used for a lithium-ion battery, and a separatorhaving an excellent ability in containing an organic electrolytesolution may be used for a lithium-ion polymer battery. For example, theseparator may be manufactured as follows.

A separator composition may be prepared by mixing a polymer resin, afiller, and a solvent. The separator composition may be directly coatedon an electrode and dried for forming the separator. Or, the separatorcomposition may be cast on a support and dried, and then a separatorfilm peeled from the support may be laminated on an electrode forforming the separator.

The polymer resin used for manufacturing the separator is notparticularly limited, and thus, any material used as a bonding materialof an electrode plate may be used. For example, vinylidenefluoride/hexafluoropropylene co-polymer, PVDF, polyacrylonitrile,poly(methyl methacrylate), or a combination thereof may be used.

Next, an electrolyte is prepared.

For example, the electrolyte may be an organic electrolyte solution. Theelectrolyte may also be a solid. For example, the electrolyte may be aboron oxide or lithium oxynitride; however, it is not limited thereto,and any solid electrolyte used in the art may be used. The solidelectrolyte may be formed on the anode using a sputtering method.

For example, an organic electrolyte solution may be prepared. Theorganic electrolyte solution may be manufactured by dissolving lithiumsalt in an organic solvent.

Any organic solvent used in the art may be used for the organic solvent.For example, propylene carbonate, ethylene carbonate, fluoroethylenecarbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate,methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate,methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate,benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran,γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide,dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane,sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethyleneglycol, dimethyl ether, or a combination thereof may be used.

Any lithium salt used in the art may be used for the lithium salt. Forexample, LiPF₆, LiBF₄, LiSbF₆, LiAsF₆, LiClO₄, LiCF₃SO₃, Li(CF₃SO₂)₂N,LiC₄F₉SO₃, LiAlO₂, LiAlCl₄, LiN(C_(x)F_(2x+1)SO₂)(C_(y)F_(2y+1)SO₂)(where x and y are natural numbers), LiCl, LiI, or a combination thereofmay be used.

As illustrated in FIG. 6, a lithium battery 1 includes a cathode 3, ananode 2, and a separator 4. The above-described cathode 3, anode 2, andseparator 4, as described above, are wound or folded to be encased in abattery case 5. Thereafter, an organic electrolyte solution is injectedinto the battery case 5 and sealed by a cap assembly 6 for completingthe lithium battery 1. The battery case 5 may have a cylindrical shape,a square shape, or a thin film shape. For example, the battery 1 may bea large thin film type battery. The battery 1 may be a lithium-ionbattery.

The separator 4 may be disposed between the cathode 3 and the anode 2 toform a battery structure. The battery structure may be layered as abicell structure and impregnated in an organic electrolyte solution, andthen an obtained structure is accommodated in a pouch and is sealed tocomplete a lithium-ion polymer battery.

Also, a plurality of the battery structures may be layered for forming abattery pack, and the battery pack may be used for any high-capacity andhigh-output devices. For example, the battery pack may be used for anotebook computer, a smartphone, or an electric vehicle.

Also, since the lithium battery has excellent storage stability, lifecharacteristics, and high rate characteristics under high temperatureconditions, the lithium battery may be used in an electric vehicle (EV).For example, the lithium battery may be used in a hybrid vehicle such asa plug-in hybrid electric vehicle (PHEV).

A method of manufacturing an electrode active material according toanother embodiment includes mixing a core including the electrode activematerial and a lithium-free oxide particle having a spinel structure;and forming a surface treatment layer including the lithium-free oxideon the core by undergoing a dry process.

The dry process includes forming a surface treatment layer, withoutusing a solvent, by inducing mechanical energy to a mixture of a coreincluding the electrode active material and a lithium-free oxideparticle.

The dry process may comprise a) a method of disposing, e.g., contactingand attaching, a powder of a covering material, for example aspinel-structured lithium-free oxide, on a surface of a core with a lowspeed ball mill and simultaneously cohering the attached particles eachother to form a surface treatment layer, b) a method of confining andattaching covering material particles on a surface of a core particle byrotation of a grinding media or a rotator disposed in an apparatus, andsimultaneously binding the covering material particles mechanically onthe core particle by stresses or binding the particles by softening orfusing a surface treatment layer of the covering material particles onthe core particle by a heat produced by the stresses, or c) a method offusing a portion or the entire surface treatment layer and the core byperforming a heat treatment on the core covered with the surfacetreatment layer formed according to the method a) and/or b) and thencooling, but the method is not limited thereto, and any dry process usedin the art may be used.

For example, the dry process may be one selected from a planetary ballmill method, a low-speed ball mill method, a high-speed ball millmethod, a hybridization method, and a mechanofusion method. For example,a mechanofusion method may be used. In the mechanofusion method, themixture is fed into a rotating container, where the mixture is subjectedto a centrifugal force and is fixed on the container inner wall, andthen the mixture is compressed in a gap between the container inner walland an arm head near the container inner wall. A mechanofusion methodcorresponds to the method b).

Performing a heat treatment on a product in which the surface treatmentlayer is formed may be further included after forming the surfacetreatment layer with the dry process. Due to the heat treatment, thesurface treatment layer may be firmer and/or more stable than before theheat treatment. A heat treatment condition that may fuse a portion orthe entire surface treatment layer may be available.

In the method above, the content of the lithium-free oxide may be about10 wt % or less, based on the total weight of both the core and thelithium-free oxide. For example, the content of the lithium-free oxidemay be about 5 wt % or less, based on the total weight of both the coreand the lithium-free oxide. For example, the content of the lithium-freeoxide may be 0 to about 10 wt %. For example, the content of thelithium-free oxide may be 0 to about 5 wt %.

The method of manufacturing the lithium-free oxide particles may includepreparing a mixture by milling a lithium-free oxide precursor; andsintering the mixture to prepare a lithium-free oxide having aspinel-structure.

In the step of preparing a mixture by milling a lithium-free oxideprecursor, intermediate phase may be prepared by pre-reacting precursorparticles through a treatment of the lithium-free oxide precursor withthe ball mill or the like. The intermediate phase may be a phaseincluding an oxide including two or more transition metals.

Since the mixture includes the intermediate phase, a formation ofvarious secondary phase, for example, a formation of impurity phases dueto ZnO volatilization during the sintering process, may be prevented.That is, due to the middle phase formation, a lithium-free oxide havinga spinel structure from which impurity phases are removed may bemanufactured even at high temperature during the sintering process.Also, due to the high temperature sintering, the crystalline propertiesof the lithium-free oxide may be improved.

After the manufacturing of the lithium-free oxide having a spinelstructure, grinding of the lithium-free oxide may be further performed.Due to the grinding, lithium-free oxide nanoparticles may be prepared.The nanoparticles may have a diameter of about 10 nm to about 1000 nm,specifically about 20 nm to about 900 nm, more specifically about 30 nmto about 800 nm.

The sintering of the mixture may be performed at a high temperature ofabout 700° C. to about 1500° C. For example, the sintering may beperformed at a temperature of about 1000° C. to about 1400° C.

As the sintering of the mixture is performed at a high temperature,properties of a surface treatment material may be convenientlycontrolled. For example, since control of the sintering temperature isconvenient, content of impurities or the like may be readily adjusted.In contrast, when the mixture is heat treated at the same time with thecore, the sintering temperature is limited to be a low temperature oflower than 700° C. to prevent deterioration of the core, so it isdifficult to control properties of a surface treatment material.

According to the foregoing method, the sintering may be performed forabout 12 to about 72 hours. For example, the sintering may be performedfor about 24 to about 60 hours. For example, the sintering may beperformed for about 36 to about 60 hours.

The sintering may be performed in an oxygen, air, or nitrogenatmosphere. For example, the sintering may be performed in an airatmosphere.

Hereinafter, the present disclosure will be described in further detailthrough examples and comparative examples. The examples and comparativeexamples are just for exemplification of the present disclosure, and thepresent disclosure shall not limited thereto.

Manufacture of Spine-Structured Lithium-Free Oxide

Preparation Example 1 (Dry Process)

Tin oxide (SnO) and zinc oxide (ZnO) were mixed at a mole ratio of about1:2 and milled at about 300 to about 500 revolutions per minute (rpm)for about 5 hours in a planetary ball mill (Fritsch, Planetary mono mill6). Subsequently, SnZn₂O₄ having a spinel structure was prepared bysintering the product at about 1200° C. for about 48 hours in air. Then,SnZn₂O₄ nanoparticles with a diameter of about 100 nm were prepared bygrinding the SnZn₂O₄ with a paint shaker for about 1 hour.

FIG. 2 shows a scanning electron microscope (SEM) image of SnZn₂O₄nanoparticles prepared in Preparation Example 1.

Comparative Preparation Example 1 (Co-Precipitation Method)

Tin chloride (SnCl₄) and zinc nitrate (Zn(NO₃)₂) in a mole ratio ofabout 1:2 were added to water to prepare a first aqueous solution. LiOHwas added to water to prepare a second aqueous solution. The first andsecond aqueous solutions were mixed to co-precipitate SnZn₂(OH)₈. Theprecipitated SnZn₂(OH)₈ was filtered, dried, and sintered at atemperature of about 850° C. in an oxygen atmosphere for about 12 hoursto manufacture SnZn₂O₄. Next, SnZn₂O₄ nanoparticles with a diameter ofabout 100 nm were prepared by grinding the SnZn₂O₄ with a paint shakerfor about 1 hour.

Manufacturing Surface-Treated 5 V Cathode Active Material

Example 1

SnO and ZnO were mixed at a mole ratio of about 1:2, and then milled atabout 300 to about 500 rpm for about 5 hours in a planetary ball mill(Fritsch, Planetary mono mill 6). Subsequently, SnZn₂O₄ having a spinelstructure was prepared by sintering the product at about 1200° C. forabout 48 hours in air. Then, SnZn₂O₄ nanoparticles with a diameter ofabout 100 nm were prepared by grinding the SnZn₂O₄ with a paint shakerfor about 1 hour.

3 parts by weight of the SnZn₂O₄ nanoparticles and 97 parts by weight ofLiNi_(0.5)Mn_(1.5)O₄ powder with an average particle diameter of 10 μmwere mixed. The LiNi_(0.5)Mn_(1.5)O₄ powder with an average particlediameter of 10 μm is shown in FIG. 3. A cathode active material of whicha surface treatment layer including SnMg₂O₄ was formed on aLiNi_(0.5)Mn_(1.5)O₄ core was prepared by putting the mixture into a drytype surface treatment device (Hosokawa Micron Corporation, Japan,Mechanofusion device, Nobilta-130) and treating at about 6000 rpm forabout 5 minutes. The prepared cathode active material is shown in FIG.4.

Example 2

A cathode active material was manufactured using the same method as inExample 1 except for using SnO and magnesium oxide (MgO) as alithium-free oxide precursor to form a surface treatment layer includingSnMg₂O₄.

Example 3

A cathode active material was manufactured using the same method as inExample 1 except for using MgO and aluminum oxide (Al₂O₃) as alithium-free oxide precursor and using a mole ratio of MgO and aluminumnitrate to form a surface treatment layer including MgAl₂O₄.

Example 4

A cathode active material was manufactured using the same method as inExample 1 except for using copper oxide (CuO) and Al₂O₃ as alithium-free oxide precursor and using a mole ratio to form a surfacetreatment layer including CuAl₂O₄.

Example 5

A cathode active material was manufactured using the same method as inExample 1 except for using ZnO and Al₂O₃ as a lithium-free oxideprecursor and using a mole ratio of ZnO and Al₂O₃ to form a surfacetreatment layer including ZnAl₂O₄.

Example 6

A cathode active material was manufactured using the same method as inExample 1 except for using nickel oxide (NiO) and Al₂O₃ as alithium-free oxide precursor and using a mole ratio of nickel oxide andAl₂O₃ to form a surface treatment layer including NiAl₂O₄.

Examples 7˜12

Cathode active materials having surface treatment layers wererespectively manufactured using the same methods as in Examples 1 to 6except that the content of the lithium oxide precursor was changed toabout 1 wt % (a mixture of 1 part by weight of the lithium-free oxideand 99 parts by weight of the cathode active material).

Examples 13˜18

Cathode active materials having surface treatment layers wererespectively manufactured using the same methods as in Examples 1 to 6except that the content of the lithium oxide precursor was changed toabout 5 wt % (a mixture of 5 parts by weight of the lithium-free oxideand 95 parts by weight of the cathode active material).

Examples 19˜24

Cathode active materials having surface treatment layers wererespectively manufactured using the same methods as in Examples 1 to 6except that the lithium oxide precursor content was changed to about 10wt % (a mixture of 10 parts by weight of the lithium-free oxide and 90parts by weight of the cathode active material).

Comparative Example 1

LiNi_(0.5)Mn_(1.5)O₄ having an average particle diameter of about 10 μmwas directly used as a cathode active material without manufacturing asurface treatment layer.

Manufacturing Surface-Treated OLO Cathode Active Material

Example 25

SnO and ZnO were mixed at a mole ratio of about 1:2, and then milled atabout 300 to about 500 rpm for about 5 hours in a planetary ball mill(Fritsch, Planetary mono mill 6). Subsequently, SnZn₂O₄ having a spinelstructure was prepared by sintering the product at about 1200° C. forabout 48 hours in air. Then, SnZn₂O₄ nanoparticles with a diameter ofabout 100 nm were prepared by grinding the SnZn₂O₄ with a paint shakerfor about 1 hour.

3 parts by weight of the SnZn₂O₄ nanoparticles and 97 parts by weight ofLi[Li_(0.05)Ni_(0.45)Co_(0.16)Mn_(0.35)]O₂ powder with an averageparticle diameter of 10 μm were mixed. A cathode active material, ofwhich a surface treatment layer including SnMg₂O₄ was formed on aLi[Li_(0.05)N_(0.45)Co_(0.16)Mn_(0.35)]O₂ core, was prepared by puttingthe mixture into a dry surface treatment device (Hosokawa MicronCorporation, Japan, Mechanofusion device, Nobilta-130) and treating atabout 6000 rpm for about 5 minutes.

Example 26

A cathode active material was manufactured using the same method as inExample 25 except for using SnO and MgO as a lithium-free oxideprecursor to form a surface treatment layer including SnMg₂O₄.

Example 27

A cathode active material was manufactured using the same method as inExample 25 except for using MgO and Al₂O₃ as a lithium-free oxideprecursor and using a mole ratio of MgO and Al₂O₃ to form a surfacetreatment layer including MgAl₂O₄.

Example 28

A cathode active material was manufactured using the same method as inExample 25 except for using CuO and Al₂O₃ as a lithium-free oxideprecursor and using a mole ratio of CuO and Al₂O₃ to form a surfacetreatment layer including CuAl₂O₄.

Example 29

A cathode active material was manufactured using the same method as inExample 25 except for using ZnO and Al₂O₃ as a lithium-free oxideprecursor and using a mole ratio of ZnO and Al₂O₃ to form a surfacetreatment layer including ZnAl₂O₄.

Example 30

A cathode active material was manufactured using the same method as inExample 25 except for using NiO and Al₂O₃ as a lithium-free oxideprecursor and using a mole ratio of NiO and Al₂O₃ to form a surfacetreatment layer including NiAl₂O₄.

Examples 31˜36

Cathode active materials having surface treatment layers wererespectively manufactured using the same methods as in Examples 25 to 30except that the content of the lithium oxide precursor content waschanged to about 1 wt % (a mixture of 1 part by weight of lithium-freeoxide and 99 parts by weight of cathode active material).

Examples 37˜42

Cathode active materials having surface treatment layers wererespectively manufactured using the same methods as in Examples 25 to 30except that the content of the lithium oxide precursor was changed toabout 5 wt % (a mixture of 5 parts by weight of lithium-free oxide and95 parts by weight of cathode active material).

Examples 43˜48

Cathode active materials having surface treatment layers wererespectively manufactured using the same methods as in Examples 25 to 30except that the content of the lithium oxide precursor was changed toabout 10 wt % (a mixture of 10 parts by weight of lithium-free oxide and90 parts by weight of cathode active material).

Comparative Example 2

Li[Li_(0.5)Ni_(0.45)Cu_(0.16)Mn_(0.35)]O₂ having an average particlediameter of about 10 μm was directly used as a cathode active materialwithout manufacturing a surface treatment layer.

Manufacturing Cathode

Example 49

A cathode active material manufactured according to Example 1, a carbonconducting agent (Ketchen Black, EC-600JD), and PVDF were mixed at aweight ratio of about 93:3:4, and then the mixture was mixed with NMP inan agate mortar to manufacture slurry. The slurry was applied on analuminum current collector having a thickness of about 15 μm to athickness of about 20 μm by using a doctor blade, was dried at roomtemperature, and then was dried again under vacuum conditions and at atemperature of about 120° C. and was rolled to form a cathode plate onwhich a cathode active material layer was formed.

Examples 50˜96

Cathode plates were manufactured using the same method as in Example 49except that cathode active materials of Examples 2 to 48 wererespectively used.

Comparative Examples 3˜4

Cathode plates were manufactured using the same method as in Example 49except that cathode active materials of Comparative Examples 1 to 2 wereused.

Manufacturing Lithium Battery

Example 97

A coin cell was manufactured using a cathode plate manufacturedaccording to Example 49, lithium metal as a counter electrode, and asolution, in which a PTFE separator and 1.3M LiPF₆ were dissolved byethylene carbonate (EC)+diethyl carbonate (DEC) (volume ratio of about3:7), as an electrolyte.

Examples 98˜144

Coin cells were manufactured using the same methods as in Example 97except that cathode plates manufactured according to Examples 50 to 96were respectively used.

Comparative Example 5˜6

Coin cells were manufactured using the same methods as in Example 97except that cathode plates manufactured according to ComparativeExamples 3 to 4 were respectively used.

Evaluation of Example 1: XRD Analysis

XRD analysis was performed on each surface of SnZn2O4 manufacturedaccording to Preparation Example 1 and the Comparative PreparationExample 1, and a result thereof is illustrated in FIG. 1A and FIG. 1B.Cu—Kα radiation was used for the XRD measurement).

FIG. 1A illustrates a result of XRD analysis of SnZn₂O₄ manufacturedaccording to Comparative Preparation Example 1.

FIG. 1B illustrates a result of XRD analysis of SnZn₂O₄ manufacturedaccording to Preparation Example 1.

As illustrated in FIG. 1B, SnZn₂O₄ of Preparation Example 1 only had acharacteristic peak corresponding to SnZn₂O₄ having a spinel structure;however, as illustrated in FIG. 1A, SnZn₂O₄ of Comparative PreparationExample 1 had many peaks corresponding to impurity phases. SnZn₂O₄ ofPreparation Example 1 practically did not include impurity phases. Thatis, intensities of peaks corresponding to impurity phases in an XRDspectrum that is measured using Ca—Kα radiation were at a level of anoise level or lower.

Also, a diffraction peak at about 34° 2θ for a (311) crystal face inFIG. 1A was shown, and a full width at half maximum (FWHM) of thediffraction peak was about 0.530°. However, a FWHM of the diffractionpeak for a (311) crystal face in FIG. 1B was about 0.260°. That is, theSnZn₂O₄ of Preparation Example 1 had significantly improved crystallineproperties compared to SnZn₂O₄ of Comparative Preparation Example 1.

Evaluation of Example 2: Inductively-Coupled Plasma (ICP) Analysis

An ICP experiment was performed on a surface of a cathode activematerial manufactured according to Example 1.

A device used to perform the ICP experiment was the model ICPS-8100 ofShimadzu Corporation. A composition ratio of Sn:Zn on the cathode activematerial surface was about 1.000:2.000.

Evaluation of Example 3: High-Temperature Stability at about 60° C.

Constant-current charging was performed on coin cells manufacturedaccording to Examples 97 to 120 and Comparative Example 5, to a voltageof 4.45 V at a rate of 0.05 C, and constant-current discharging wasperformed to a voltage of 3.0 V at a rate of 0.05 C in a first cycle. Ina second cycle, constant-current charging was performed to a voltage of4.45 V at a rate of 0.1 C, and then constant-voltage charging wasperformed until a current became 0.05 C while maintaining a voltage at4.45, and constant-current discharging was performed to a voltage of 3.0V at a rate of 0.1 C. In a third cycle, constant-current charging wasperformed to a voltage of 4.45 V at a rate of 0.5 C, and thenconstant-voltage charging was performed until a current became 0.05 Cwhile maintaining a voltage at 4.45 V, and constant-current dischargingwas performed to a voltage of 3.0 V at a rate of 0.2 C. In the thirdcycle, discharge capacity was considered as standard capacity.

In a fourth cycle, a charging operation was performed to a voltage of4.45 V at a rate of 0.5 C, and then constant-voltage charging wasperformed until a current became 0.05 C while maintaining a voltage at4.45 V. Thereafter, the charged batteries were stored in an oven at atemperature of about 60° C. for about seven days, and then were removedto be discharged to a voltage of 3.0 V at a rate of 0.1 C. Some resultsof the charging and discharging operations are shown in Table 1 below. Acapacity retention ratio after high temperature storage is defined asexpressed in the following Equation 1.Capacity retention ratio after high temperature storage[%]=dischargecapacity after high temperature storage in a fourth cycle/standardcapacity×100%,  Equation 1

wherein the standard capacity is a discharge capacity in a third cycle.

Evaluation of Example 4: High-Temperature Stability about 90° C.

The stability experiment was performed on coin cells manufacturedaccording to Examples 97 to 120 and Comparative Example 5 using the samemethod as in the Evaluation of Example 3 except that the chargedbatteries were stored in an oven at a temperature of about 90° C. forabout 4 hours. Some results of the charging and discharging operationsare shown in Table 1 below. A capacity retention ratio after hightemperature storage is defined as expressed in Equation 1 above.

TABLE 1 Capacity retention ratio Capacity retention ratio after storageat 60° C. after storage at 90° C. for for 7 days [%] 4 hours [%]Comparative 1.7 58.2 Example 5 Example 97 43.7 77.7 Example 98 41.6 75.6

As shown in Table 1, capacity retention ratios after high temperaturestorage of the lithium batteries of Examples 97 to 98 were significantlyimproved in comparison with the lithium batteries of Comparative Example5. That is, stability at high temperature of the lithium batteries ofExamples 97 to 98 was significantly improved.

Evaluation of Example 7: High Temperature Charge/Discharge Experiment

Coin cells manufactured according to Examples 97 to 120 and ComparativeExample 5 were charged/discharged 100 times with a constant current ofabout 1 C rate in the voltage range of 3.5 V to 4.9 V (vs. Li) at a hightemperature of about 60° C. A capacity retention ratio in a 100^(th)cycle is calculated from the following Equation 2. An initial coulombicefficiency is defined as expressed in Equation 3. The capacity retentionratios and the initial coulombic efficiencies in a 100^(th) cycle areshown in Table 2.Capacity retention ratio in 100^(th) cycle[%]=discharge capacity in100^(th) cycle/discharge capacity in 1^(st) cycle×100%  Equation 2Initial Coulombic Efficiency[%]=discharge capacity in 1^(st)cycle/charge capacity in 1^(st) cycle×100%  Equation 3

TABLE 2 Retention ratio in Initial coulombic 100^(th) cycle [%]efficiency [%] Comparative Example 5 74.4 89.5 Example 97 81.8 93.8Example 98 83.1 94.4

As shown in Table 2, the lithium batteries of Examples 97 to 98 showedimproved high temperature life characteristics and initial coulombicefficiencies in comparison with the lithium battery of ComparativeExample 5.

Evaluation of Example 6: High Rate Characteristics Analysis

Coin cells manufactured according to Examples 97 to 98 and ComparativeExample 5 were charged with a constant current of about 0.1 C rate inthe voltage range of about 3.5 V to about 4.9 V (vs. Li) at roomtemperature and a capacity retention ratio according to increasedcurrent density is shown in FIG. 4. Current densities during dischargewere about 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C, 5 C, 8 C and 10 C raterespectively. In FIG. 5, a capacity retention is calculated from thefollowing Equation 4.Capacity retention ratio for each rate[%]=discharge capacity for eachrate/discharge capacity at 0.1 C×100%  Equation 4

As shown in FIG. 5, high rate characteristics of the lithium batteriesof Examples 97 to 98 were improved in comparison with the lithiumbatteries of Comparative Example 5.

As described above, according to the one or more of the above Examples,since a core capable of intercalating and deintercalating lithium issurface-treated with a spinel-structured lithium-free oxide excludingimpurity phases, high temperature stability, high temperature lifecharacteristics, and high rate characteristics of a lithium battery maybe improved.

It should be understood that the exemplary embodiments described thereinshould be considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould be considered as available for other similar features or aspectsin other embodiments.

What is claimed is:
 1. An electrode active material, consisting of: acore capable of intercalating and deintercalating lithium; and a surfacetreatment layer that completely covers the core, wherein the surfacetreatment layer comprises a lithium-free oxide having a spinelstructure, and an intensity of an X-ray diffraction peak correspondingto impurity phases of the lithium-free oxide, when measured using Cu—Kαradiation, is at a noise level of an X-ray diffraction spectrum or less,wherein, the lithium-free oxide is one or more selected from SnMg₂O₄SnZ₂O₄, MgAl₂O₄, CuAl₂O₄, Zn Al₂O₄ and NiAl₂O₄, and wherein the corecomprises one or more compounds selected from compounds expressed by thefollowing Formulas 4 to 8:Li_(x)Co_(1−y)M_(y)O_((2−α))X_(α),  Formula 4Li_(x)Co_((1−y−z))Ni_(y)M_(z)O_((2−α))X_(α),  Formula 5Li_(x)Mn_((2−y))M_(y)O_((4−a))X_(α),  Formula 6Li_(x)Co_((2−y))M_(y)O_((4−α))X_(α), and  Formula 7Li_(x)Me_(y)M_(z)PO_((4−α))X_(α)  Formula 8 wherein 0.90≤x≤1.1, 0≤y≤0.9,0≤z≤0.5, (1−y−z)>0, 0≤α≤2; Me is one or more metals selected from Ti, V,Cr, Mn, Fe, Co, Ni, Cu, Al, Mg, Zr, and B; M is one or more elementsselected from Mg, Ca, Sr, Ba, Ti, Zr, Nb, Mo, W, Zn, Al, Si, Ni, Mn, Cr,Fe, Mg, Sr, V, and a rare-earth element; and X is an element selectedfrom O, F, S, and P.
 2. The electrode active material of claim 1,wherein the lithium-free oxide has an X-ray diffraction peak at about35.5°±2.0° two-theta for a peak corresponding to a (311) crystal face,when measured using Cu—Kα radiation, and a full width at half maximum ofthe X-ray diffraction peak corresponding to the (311) crystal face isless than 0.3° two-theta.
 3. The electrode active material of claim 1,wherein the lithium-free oxide has an X-ray diffraction peak at about35.5°±2.0° two-theta for a peak corresponding to a (311) crystal face,when measured using Cu—Kα radiation, and a full width at half maximum ofthe X-ray diffraction peak corresponding to the (311) crystal face isabout 0.220° two-theta to about 0.270° two-theta.
 4. The electrodeactive material of claim 1, wherein a ratio of an intensity of an X-raydiffraction peak corresponding to a (440) crystal face to an intensityof an X-ray diffraction peak corresponding to a (311) crystal face isabout 0.3 or more.
 5. The electrode active material of claim 1, whereina ratio of an intensity of an X-ray diffraction peak corresponding to a(511) crystal face to an intensity of an X-ray diffraction peakcorresponding to a (400) crystal face is about 0.25 or more.
 6. Theelectrode active material of claim 5, wherein a ratio of an intensity ofan X-ray diffraction peak corresponding to a (511) crystal face to anintensity of an X-ray diffraction peak corresponding to a (440) crystalface is about 0.5 or more.
 7. The electrode active material of claim 5,wherein a content of the lithium-free oxide is about 10 weight percentor less, based on a total weight of the electrode active material. 8.The electrode active material of claim 5, wherein a thickness of thesurface treatment layer is about 1 angstrom to about 1 micrometer.
 9. Anelectrode comprising an electrode active material according to claim 5.10. A lithium battery comprising an electrode according to claim 9.